When dialling a non-UK number, such as an international destination you will need to dial with the international prefix without the leading zeroes (“00”).
For example:
USA +1-202-555-0195 or 001-202-555-0195 should be dialled as 1-202-555-0195
Netherlands +31-202-555-0195 or 0031-202-555-0195 should be dialled as 31-202-555-0195
You can check all the international dial codes from your account by visiting this link: Customer Rates